html{
	height: 100%;
}
body{
	margin: 0;
	padding: 0;
	font-family: sans-serif;
	background: linear-gradient(#243b55,#cecece);//线性渐变
}
.login_box{
	position: absolute;
	top: 50%;
	left: 50%;
	width: 25rem;
	padding: 2.5rem;
	transform: translate(-50%,-50%);
	background: rgba(56, 130, 255,0.5);
	box-sizing: border-box;
	box-shadow: 0 15px 25px rgba(255, 255, 255,0.6);
	border-radius: 10px;
}
/*login样式*/
.login_box h2{
	margin: 0 0 30px;
	padding: 0;
	color: #fff;
	text-align: center;
}
/*相对定位*/
.login_box .user_box{
	position: relative;
}
/*input*/
.login_box .user_box input{
	width: 100%;
	padding: 10px 0;
	font-size: 1rem;
	color: #fff;
	margin-bottom: 1.875rem;
	border: none;
	border-bottom: 1px solid #fff;
	outline: none;
	background: transparent;
}
.login_box .user_box label{
	position: absolute;
	top: 0;
	left: 0;
	padding: 10px 0;
	font-size: 1rem;
	color: #fff;
	pointer-events: none;
	transition: 0.5s;
}
.login_box .user_box input:focus ~label,
.login_box .user_box input:valid ~label{
	top: -20px;
	left: 0;
	color: #03e9f4;
	font-size: 12px;
}
.login_box form a{
	position: relative;
	display: inline-block;
	padding: 10px 20px;
	color: #03e9f4;
	font-size: 16px;
	text-decoration: none;
	text-transform: uppercase;
    overflow: hidden;
	transform: 0.5s;
	margin-top: 40px;
	letter-spacing: 4px;
}
.login_box a:hover{
	background: #03E9F4;
	color: #fff;
	border-radius: 5px;
	box-shadow: 0 0 5px #03E9F4,
				0 0 25px #03E9F4,
				0 0 50px #03E9F4,
				0 0 100px #03E9F4;
}
.login_box a span{
	position: absolute;
	display: block;
}
.login_box a span:nth-child(1){
	top: 0;
	right: -100%;
	width: 100%;
	height: 2px;
	background: linear-gradient(90deg,transparent,#03e9f4);
	animation: bth-anim1 1s linear infinite
}
@keyframes  bth-anim1{
	0%{
		left: -100%;
	}
	50%,100%{
		left: 100%;
	}
}
.login_box a span:nth-child(2){
	top: -100%;
	right: 0;
	width: 2px;
	height: 100%;
	background: linear-gradient(180deg,transparent,#03e9f4);
	animation: bth-anim2 1s linear infinite;
	animation-delay: 0.25s
}
@keyframes  bth-anim2{
	0%{
		top: -100%;
	}
	50%,100%{
		top: 100%;
	}
}
.login_box a span:nth-child(3){
	bottom: 0;
	right: -100%;
	width: 100%;
	height: 2px;
	background: linear-gradient(270deg,transparent,#03e9f4);
	animation: bth-anim3 1s linear infinite;
	animation-delay: 0.5s
}
@keyframes  bth-anim3{
	0%{
		right: -100%;
	}
	50%,100%{
		right: 100%;
	}
}
.login_box a span:nth-child(4){
	bottom: -100%;
	left: 0;
	width: 2px;
	height: 100%;
	background: linear-gradient(360deg,transparent,#03e9f4);
	animation: bth-anim4 1s linear infinite;
	animation-delay: 0.75s
}
@keyframes  bth-anim4{
	0%{
		bottom: -100%;
	}
	50%,100%{
		bottom: 100%;
	}
}
#a2{
	float: right;
}







































